Powertrain with series electric launch and electric power assisted performance

Abstract

A powertrain includes an engine with an engine output member, such as a crankshaft, and a first motor / generator having a first rotor connected to the crankshaft for rotation therewith. A transmission includes a transmission input member, a transmission output member, and a differential gearing arrangement selectively operatively connecting the transmission input member and the transmission output member. A plurality of torque transmitting devices is selectively engageable to provide a plurality of fixed speed ratios between the transmission input member and the transmission output member. A second motor / generator includes a second rotor connected to the gearing arrangement to provide torque to the transmission output member. The transmission input member is selectively connectable to the engine output member and the first rotor to alternate between a series hybrid drive mode and a fixed ratio mode of powertrain operation. A corresponding method is also provided.

Description

TECHNICAL FIELD [0001] This invention relates to hybrid powertrains having an engine, a transmission, and two motor / generators, and characterized by a series hybrid mode and fixed ratio mode of operation. BACKGROUND OF THE INVENTION [0002] Electrically variable vehicle transmissions (EVTs), such as those described in U.S. Pat. No. 5,931,757, employ two electric motor / generators. The electric motor / generators are coaxially oriented with an input shaft connectable to an engine, an output shaft, and a plurality of planetary gearsets each having respective first, second, and third members. Each motor / generator is operatively connected to a respective member of one of the planetary gearsets to provide a range or mode of transmission operation characterized by a continuously variable speed ratio between the input shaft and the output shaft. The continuously variable speed ratio is proportional to the speed of one of the motor / generators. [0003] In light vehicles using gasoline or hydrogen...

AI Technical Summary

Benefits of technology

[0006] The fixed-ratio mode of operation enables power transmission from the engine to the transmission output member without engagement of the motor / generators, thereby eliminating or minimizing electrical losses. Furthermore, the first motor / generator may be significantly smaller than the motor / generators typically used in other electrically variable transmissions. The direct connection of the first motor / generator to the engine output member enables the first motor / generator to start the engine.

[0007] The first motor / generator may be used for engine inertial energy absorption whereby the first motor / generator absorbs power from the engine during shifts between fixed speed ratios. The first motor / generator converts mechanical energy from the engine to electrical energy, which is then stored in an energy storage device and later used to power the electric motor / generators. The engine inertial energy absorption enables a reduction in clutch size and clutch wear. Reduced clutch size results in reduced spin losses in the transmission.

Problems solved by technology

Reduced clutch size results in reduced spin losses in the transmission.

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